• First consider the major functions within a company,
• All of these functions generate and use common information which must be communicated between departments.
• Since computers handle information, we must be aware of what we get, and what we produce.
• Previous paper based systems provided support for data transfer between departments, and provided a good basis for the introduction of computers
• ASIDE: Computers can make a good system better, but they will always make a bad system worse. This is because a system which is not well defined and poorly understood cannot be programmed, or optimized.
• Characteristics of paper based manufacturing systems,
Multiple copies of same information.
Revising information is hard when multiple copies exist.
Delays for the transfer of paper.
• Computers overcome and reduce the problems above, but introduce some technological challenges,
Creating programs to support corporate functions.
Software to support interdepartmental communication and data sharing.
Hardware to support the software.
• This figure below shows various departments, and the information flow [source: ???
• Requirements for interfacing corporate management and staff functional entities to the factory [source: find]
• Assumed functional hierarchy computer system structure for a large manufacturing complex [source: find]
• Report interfacing to corporate management and staff functional entities from the factory [source: find]
• The Shop Floor Production Model (SFPM):
The ISO Reference Model for Factory Automation adds a couple of layers
• A LAN (Computer Network) Hierarchy for Shop Floor Control [source: find]
• Typical Architecture for Manufacturing Components [ update]
|
Robot tended Machine Center, Cartrac Material Handling System |
|||
|
Mark Century 2000, Accuramatic 9000, Custom-single-board system. |
|||
|
Single-board processors, Machine tool controller, Servo-Controller, etc |
|||
• Functional Breakdown of Control Architecture
• In all of these models we must consider the value of the information being passed. At the low level control stages, information that is more than a few seconds old may be completely worthless, while the same information at the higher level may be valuable for quality tracking months later.
• We can draw part of a simple flow chart that illustrates a simple CIM system. The elements shown include a PLC, NC machine, and stand alone sensors. These are all integrated by a single computer running cell control software.
• The nature of Batch processes,
Batch processes deal with discrete quantities of raw materials or products.
batch processes allow the tracking of these discrete quantities of materials or products
batch processes allow more than one type of product to be processed simultaneously, as long as the products are separated by the equipment layout.
Batch processes entail movement of discrete product from processing area to processing area
Batch processes have recipes (or processing instructions) associated with each load of raw material to be processed into product.
Batch processes have more complex logic associated with processing than is found in continuous processes
Batch processes often include normal steps that can fail, and thus also include special steps to be taken in the event of a failure.
• The nature of steps in a batch process,
Each step can be simple or complex in nature, consisting of one or more operations
Generally, once a step is started it must be completed to be successful.
It is not uncommon to require some operator approval before leaving one step and starting the next.
There is frequently provision for non-normal exits to be taken because of operator intervention, equipment failure or the detection of hazardous conditions.
Depending on the recipe for the product being processed, a step may be bypassed for some products.
The processing operations for each step are generally under recipe control, but may be modified by operator override action.
Problem 7.1 List 5 industries that are well suited to integration, and 5 that are not. Indicate why you think so.
Problem 7.2 In an automated factory there as many as six levels of control. Discuss the equipment available in the lab and how this relates to the 6 level model of factor floor control.
Problem 7.3 Information drives an automated factory from the initial entry of geometry in CAD, to the final production of parts with CAM. Discuss how data networks support this and the impact of open network standards.